Glow plug timer



Jan. 20, 1970 J. P. WELSH GLOW PLUG TIMER Filed Feb. '7, 1968 TIME o I o I I I a INVENTOR -25 0 25 50 75 TEMP JAMES P. WELSH ATTORNEYS United States Patent 3,490,427 GLOW PLUG TIMER James P. Welsh, Morton, Ill., assignor to Caterpillar Tractor Co., Peoria, Ill., a corporation of California Filed Feb. 7, 1968, Ser. No. 703,718 Int. Cl. F0211 17/02; F02b 9/08 US. Cl. 123-179 1 Claim ABSTRACT OF THE DISCLOSURE A diesel engine precombustion chamber automatic heating device having an electromagnetic circuit breaker manually actuated so as to commence the heating of the chambers and thermostatically released upon the attainment of a predetermined temperature in the chambers.

Starting a diesel engine is often a rather difficult task when the ambient temperature is low. In order to ease this difficulty, it has become known that a warming of the combustion or precombustion chambers will reduce the time and energy required to start the engine.

Of the many ways to heat the chambers of an engine, the use of glow plugs has become very prevalent. However, the length of time a glow plug must be energized to provide a properly heated chamber is dependent upon the ambient temperature at which the diesel engine will be started. In engines using the glow plugs, it has been found that vehicle operators often are unable to accurately judge the time required for the glow plugs to be energized. This results in improper heating of the precombustion chambers and hard starting is encountered in spite of the glow plugs.

Thus it has become almost imperative that a timing device be provided so that an accurate energization time may be obtained. The timing devices heretofore known, however, have proven to be highly complicated and expensive mechanisms.

It is therefore an object of the instant invention to provide a means to improve the starting characteristics of an internal combustion engine.

It is an object of this invention to provide a device for accurately heating the precombustion chamber of an internal combustion engine so as to produce satisfactory starting characteristics in that engine.

It is also an object of this invention to provide a device which will automatically discontinue the heating of the precombustion chambers when the desired temperature has been reached.

It is a further object of this invention to provide an inexpensive and simple mechanism for warming the precombustion chambers of an internal combustion engine to a predetermined temperature while obviating the problem of operator error.

Other objects of the invention will become apparent to those skilled in the art upon reading the following description with reference to the accompanying drawing.

In the drawing:

FIG. 1 shows a sectional side view of the preferred embodiment of the invention;

FIG. 2 shows a schematic diagram of the electrical circuitry of the invention; I

FIG. 3 shows a view of the device taken along the line III--III of FIG. 1; and

FIG. 4 is a graph showing the relationship between ambient temperature and time required for heating the precombustion chambers of the engine.

Referring now to the drawing in greater detail, there is shown in FIG. 1 a timing mechanism 11 having a housing 13 which is suitably secured to a support member 15. Extending longitudinally through a portion of the 3,490,427 Patented Jan. 20, 1970 ice housing, a control rod 17 is held in the position shown in FIG. 1 by a detent 19 which is biased into a groove 21 in the rod by a spring 23.

When rod 17 is moved to the right as shown in the drawing, the detent 19 is forced out of the groove and an end 25 of the rod slidable within a coil 27 aligns with the coil and compresses a spring 29 disposed between end 25 and a face 31 of the housing.

A contact assembly 35 is mounted on rod 17 consisting of an insulator 37 and a contact plate 39. The assembly 35 is urged against a shoulder 41 of the end 25 of rod 17 by a spring 43 disposed between the insulator 37 and a cup-shaped spring holder 45 which is, in turn, biased to its holding position by a spring 47.

Rightward movement of the rod 17 causes the contact plate 39 to enter into contact with electrical terminals 51 and 53. Referring to FIG. 2, the cooperation of plate 39 with contacts 51 and 53 causes the completion of a circuit between a battery 55 and glow plugs 57. One end of coil 27 is also energized by the contact of the plate 39 with terminal 53, as is a resistor 59 in a fixed temperature thermostat 61. The other end of coil 27 is connected to a thermal disc 63 in the thermostat and the resistor and disc are grounded as shown at 65.

As current flows through the coil 27, the end 25 of the rod is restrained in the rightward position and contact plate 39 is held in contact with terminals 51 and 53. Current passing through resistor 59 in the thermostat causes heat to be generated and at a predetermined temperature, thermal disc 63 will snap to an open position breaking ground contact of the coil 27. The biasing force of spring 29 will then urge rod 17 to the left until detent 19 again enters groove 21.

When this snap action has occurred, rod 17 may then be manually moved to the left as shown in the drawing, bringing contact plate 39 into contact with terminals 71 and 73. This causes completion of an electrical circuit from battery 55 to the starting motor 75 and the starting motor begins to crank the engine for starting.

When contact plate 39 contacts terminals 71 and 73, it will also come into contact with a third set of terminals 77 and 79 and the contact with terminal 79 will cause a continuation of the heating by the glow plugs until the engine is started and the rod 17 is returned once again to the central position of FIG. 1.

As shown in FIG. 4, as the ambient temperature in creases, the amount of time required for heating by the glow plugs is decreased. This relationship is a function of the fixed temperature thermostat '61 so that when the suitable starting temperature in the precombustion chamber has been attained, thermal disc 63 will snap open releasing rod 17.

Thus applicant has provided a new and improved glow plug timing device which presents a true advancement in the art in view of its dependability, simplicity, and low cost of manufacture.

I claim:

1. A glow plug actuating and timing device comprising a housing,

a coil fixedly mounted within the housing,

a spring mounted within the coil and abutting a face of said housing,

a manually actuatable rod extending into said housing and abutting said spring in axially slidable relationship relative to said coil,

means within said housing for biasing said rod to a first position,

means for positively retaining said rod in said first position,

a contact member mounted on said rod,

a first set of contacts in said housing for cooperation with said contact member to actuate said coil when the rod is moved to a second position by forceably overcoming said positive retaining means and said spring whereby said rod is retained in said second position by the magnetic field of said coil,

at least one glow plug electrically connected to said first set of contacts for actuation when said rod is moved to said second position,

a heat generating device similarly connected to said first set of contacts in parallel relationship with said at least one glow plug,

a switch actuated to an open position by the heat generated by said heat generating device at a predetermined temperature thereof, said switch being in series relationship with said coil, and said switch and coil being in parallel relationship with said heat generating device and with said at least one glow plug, whereby actuation of said switch opens the electrical circuit of said coil and said biasing means motivate said rod into said first position,

an engine starter motor,

a second set of contacts in said housing for cooperation with said contact member to actuate said starter motor when the rod is moved to a third position by forceably overcoming said positive retaining means, and

means connecting said at least one glow plug to said second set of contacts for actuation thereof while said starter motor is being actuated.

References Cited UNITED STATES PATENTS 1,710,884 4/1929 Mackie 335-145 XR 2,611,843 9/1952 Bourne 335-107 3,089,475 5/1963 Kohler et a1. 123179 LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. 

